Potential role of ferritin heavy chain in oxidative stress and apoptosis in human mesothelial and mesothelioma cells: implications for asbestos-induced oncogenesis

Our plain-English summary of Potential role of ferritin heavy chain in oxidative stress and apoptosis in human mesothelial and mesothelioma cells: implications for asbestos-induced oncogenesis, by W. Aung, S. Hasegawa, T. Furukawa, et al (Carcinogenesis, 2007).

The study

• Authors: W. Aung, S. Hasegawa, T. Furukawa, T. Saga
• Journal: Carcinogenesis
• Published: 2007;28(9):2047-52
• Cited by: 53 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Exposure to asbestos is a known etiological factor in malignant mesothelioma (MM). However, in vitro cell culture studies have provided paradoxical evidence that asbestos exposure to mesothelial cells causes cytotoxicity or apoptosis rather than malignant transformation. Although it has been shown that the iron associated with asbestos participates in the cell toxicity and probably MM pathogenesis via generation of reactive oxygen species (ROS), the molecular mechanisms largely remain unknown. Here, we demonstrate that ferritin heavy chain (FHC), a core subunit of iron-binding protein ferritin, works as an anti-apoptotic protein against toxic asbestos and oxidative stress in human mesothelial cells and MM cells. We found that FHC was induced in asbestos-exposed MeT-5A human mesothelial cells. The mesothelial cell line stably expressing FHC generated less amount of hydrogen peroxide (H2O2), one of the main ROS, after asbestos exposure and was more resistant to apoptosis induced by H2O2 compared with the cells transfected with the empty vector. Next, we investigated biological roles of FHC in human MM cell. We found that NCI-H2052, a human MM cell line, had a higher expression of endogenous FHC than MeT-5A and used the cell to address FHC function in MM. NCI-H2052 showed reduced H2O2 production and an apoptosis-resistant phenotype compared with MeT-5A. Suppression of the over-expressed FHC by using FHC small interfering RNA rendered the MM cells sensitive to apoptosis, suggesting the contribution of FHC to apoptosis resistance of the MM cells. Our findings highlight the potential role of FHC in the pathogenesis of asbestos-induced mesothelioma.

In plain English

This was a laboratory study of cell lines; no people or animals were studied. The authors exposed MeT-5A, an immortalized human pleural mesothelial cell line, to crocidolite and chrysotile and measured ferritin heavy chain (FHC), a subunit of the iron-binding protein ferritin. Crocidolite raised FHC with dose, starting within 1 hour. Chrysotile raised it less, and crocidolite stripped of iron by the chelator DFO induced less. Cells engineered to make extra FHC showed a smaller rise in hydrogen peroxide after asbestos exposure. In representative experiments after hydrogen peroxide treatment, these cells had fewer apoptotic (programmed cell death) or dead cells than controls: 23.1 versus 43.6% at 0.5 mM and 34.4 versus 48.0% at 1 mM. The mesothelioma line NCI-H2052, highest in FHC of those tested, likewise had fewer than MeT-5A (17.9 versus 53.1% and 20.3 versus 61.4%). After hydrogen peroxide, NCI-H2052 cells given FHC-lowering siRNA had more apoptotic cells than those given control siRNA (52.8 versus 48.8% and 58.1 versus 49.3%). The authors concluded that FHC works against apoptosis in these cells, noting the shift was partial, which may indicate other molecules are involved.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) cell culture experiments using human mesothelial and mesothelioma cell lines
• Who was studied: No human subjects. The study used the immortalized human pleural mesothelial cell line MeT-5A, MeT-5A lines engineered to over-express FHC (MeT-FHC) or carrying an empty vector (MeT-Hyg), and the malignant mesothelioma cell lines NCI-H2052, NCI-H226, NCI-H28, NCI-H2452 and ACC-MESO-1. Work was done at the National Institute of Radiological Sciences, Chiba, Japan.
• Exposure: Crocidolite (Cape, South Africa, 2–30 µm long, more than 99% pure) and chrysotile (California, less than 5 µm long, more than 95% pure). FHC experiments used 1, 2, 5 and 10 µg/cm2. Hydrogen peroxide experiments used 6, 12 and 24 µg/cm2 of fibers. Some tests used crocidolite with its iron removed by the chelator deferoxamine (DFO). Apoptosis was induced with hydrogen peroxide at 0.5 and 1 mM.
• Main results:
  • In MeT-5A mesothelial cells, crocidolite induced FHC in a dose-dependent way. Chrysotile also appeared to, but less than crocidolite.
  • With crocidolite (5 µg/cm2), FHC in MeT-5A rose within 1 hour and increased to a sustained level over the 48 hours observed.
  • Crocidolite pre-treated with the iron chelator DFO (5 and 10 µg/cm2) induced less FHC in MeT-5A than untreated fiber at the same doses.
  • Hydrogen peroxide generation rose with crocidolite dose in both engineered cell lines. The percent increase was smaller in FHC-over-expressing MeT-FHC cells than in control MeT-Hyg cells.
  • After hydrogen peroxide treatment, apoptotic cells (early plus late, including dead cells) in representative flow cytometry experiments were 23.1% in MeT-FHC versus 43.6% in MeT-Hyg at 0.5 mM, and 34.4% versus 48.0% at 1 mM.
  • Of the mesothelioma cell lines tested, NCI-H2052 had the highest FHC, higher than non-malignant MeT-5A.
  • Not all of the mesothelioma cell lines over-expressed FHC, and levels varied among them.
  • The percent increase in hydrogen peroxide generation after crocidolite and chrysotile exposure was smaller in NCI-H2052 than in MeT-5A.
  • After hydrogen peroxide treatment, apoptotic cells in representative experiments were 17.9% in NCI-H2052 versus 53.1% in MeT-5A at 0.5 mM, and 20.3% versus 61.4% at 1 mM.
  • After 0.5 and 1 mM hydrogen peroxide, NCI-H2052 cells given FHC siRNA had a larger apoptotic population than cells given control siRNA: 52.8 versus 48.8% and 58.1 versus 49.3%. The figure shows representative results of four independent experiments.
• The authors' conclusion: The authors concluded that FHC rises as an acute response of human mesothelial cells to asbestos. They also concluded that FHC acts against apoptosis caused by oxidative stress, both in mesothelial cells and in mesothelioma cells.
• Limitations the authors state:
  • The authors did not profile other apoptosis-related genes in NCI-H2052, so they could not conclude that its apoptosis resistance depends only on FHC.
  • Lowering FHC only partly shifted NCI-H2052 cells toward apoptosis, which the authors said may mean other molecules are also involved.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Ferritin, Oxidative Stress, Apoptosis, Mesothelioma, Oncogenesis, Malignant Mesothelioma, Asbestos Exposure, Mesothelial Cells.

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